1. Technical Field
The present invention relates to printed circuit boards, particularly to an adhesive layer and a printed circuit board assembly having the adhesive layer.
2. Description of Related Art
In recent years, flexible printed circuit boards (FPCBs) are widely used in electronic devices for electrical connection due to their flexibility and lightness. Flexible printed circuit boards can be bent into various shapes adapted to being used for various electronic devices.
Generally, a double-sides adhesive tape can be used to fix a bended flexible printed circuit board. Referring to FIG. 7, a typical flexible printed circuit board 10 shaped in a folding manner is shown. The flexible printed circuit board 10 includes a first portion 11, a second portion 13 and a bending portion 12 interconnecting the first portion 11 and the second portion 12. The flexible printed circuit board 10 is bent into a U-shaped figuration with the second portion 13 overlapping the first portion 11 via bending of the bending portion 12. A double-sided adhesive tape 14 with two opposite adhesive surfaces (not labeled) is provided between the second portion 13 and the first portion 11. The two opposite adhesive surfaces of the double-sided adhesive tape 14 adhere to the first portion 11 and the second portion 13 respectively so that the second portion 13 is jointed with the first portion 11. Thus, the flexible printed circuit board 10 can maintain the folded structure.
However, an adhesion force between the double-sided adhesive tape 14 and the first board 11 and that between the double-sided adhesive tape 14 and the second board 13 are unsatisfactory, especially due to deterioration over time. Thus, a rebound force of the bending portion 12 can cause distortion of the flexible printed circuit board 10. For example, referring to FIGS. 8 and 9, the double-sided adhesive tape 14 is prone to being separated from the first portion 11 or the second portion 13. Thus, quality and performance of the electronic devices using such flexible printed circuit board 10 will be lowered.
What is needed, therefore, is an adhesive layer and a printed circuit board assembly having the adhesive layer, thereby preventing the printed circuit board assembly from distortion.